Modelling the influence of stress-strain history on the initial shear stiffness of an unsaturated compacted silttress

The manuscript is the follow-up to Vassallo et al. 2007 (Canadian Geotechnical Journal 44 - pp. 447–462), which discussed the experimentally observed small strain behaviour of an unsaturated compacted silt. The influence that matric suction and, more in general, mean net stress – matric suction history has on the initial shear stiffness was analysed and ascribed to the accumulation of irreversible volumetric strains. In this study, a model able to predict the observed behaviour is proposed, based on classical unsaturated soil volumetric hardening elastoplastic formulations. Starting from the interpretation of the results relative to simple stress paths, such as preliminary equalization and loading–unloading compression, the results of “complex” stress paths, such as those including drying–wetting cycles, have subsequently been modelled by introducing some additional parameters.